This study reconstructs sea surface temperatures (SSTs) and coastal environmental conditions during the Last Interglacial (MIS 5e) and the Holocene using delta 18O and delta 13C values of fossil marine molluscs from Yorke Peninsula, southern Australia. A total of 148 MIS 5e and 53 Holocene specimens were analysed. MIS 5e SSTs ranged from 17.6 f 0.8 degrees C to 22.9 f 0.9 degrees C, whereas the Holocene SSTs ranged from 15.7 f 0.9 degrees C to 23.0 f 1.6 degrees C. Paired comparisons between co-occurring species indicate that SSTs during MIS 5e were broadly comparable to those of the Holocene, with both periods exhibiting temperatures up to 4 degrees C higher than modern values at their warmest. In contrast, delta 13C values for MIS 5e are consistently lower than those of the Holocene, consistent with increased freshwater input and wetter regional conditions. These results provide the first geochemical evidence for comparable SSTs but increased precipitation and runoff along the southern Australian coast during MIS 5e, offering rare quantitative constraints on how coastal environments in this region responded to interglacial conditions.

Optically stimulated luminescence (OSL) dating has been applied to the Ngankipari Formation, a weakly consolidated calcareous and silty sand that occurs in a succession of Quaternary terrestrial sediments in the Noarlunga Embayment of the Cenozoic Saint Vincent Basin, South Australia. The dating has identified two informal members at two separate sites: a younger dated at 262 +/- 26 ka and 253 +/- 31 ka and an older dated at 381 +/- 27 ka. These OSL ages are significantly older than the early Holocene and late Pleistocene ages previously suggested for the Ngankipari Formation and have clarified its stratigraphic position in relation to other Quaternary formations, some of which have previously published OSL ages. The ages of the two members also broadly correspond with sea-levels lower than at present, Marine Isotope Stage 8 and the falling stage sea-level phase in late MIS 11, respectively. These were glacial and interstadial phases when the local gulfs and continental shelf were subaerially exposed, thereby supplying a source for windborne sediments to the terrestrial realm. The Ngankipari Formation is redefined to exclude Holocene unconsolidated surficial sediments that were mapped as part of the Ngankipari Sand in its original definition.

The essence of stories of human-environment interactions can be preserved in oral contexts for millennia, creating novel opportunities for humanizing the past. This study examines stories (knowledge-rich narratives) about the ancestral being Ngurunderi, told by Ngarrindjeri peoples of South Australia. Three elements of the Ngurunderi narrative are considered. The first recalls his journey along a 170-km long coastal barrier (Younghusband Peninsula) when this was continuous. The second discusses Ngurunderi's encounters with what are now islands off the Fleurieu Peninsula, some of which he created, interpreted as memories of when sea level was lower and "islands" were contiguous with the mainland. The third refers to the crossing of a land connection between modern Kangaroo Island and the Fleurieu Peninsula, later submerged to form Backstairs Passage. Using paleogeographic data, the most recent times at which each narrative element could have taken place and observed by people are estimated. This research suggests that: (1) stories about Younghusband Peninsula may be >6700 years cal BP; (2) islands off the Fleurieu Peninsula were created 6800-10,400 cal BP; and (3) submergence of Backstairs Passage occurred 11,000-10,100 cal BP. Narratives are linked to the period of early Holocene sea-level rise, the rapid 8200-cal BP sea-level rise event, and stabilization of sea level 7000-6000 cal BP. These narratives humanize the past and provide information that can be interpreted as both observed coastal and seascape changes as well as past human responses to rising sea level that can inform our future encounters with coastal-landscape change.

A high-level coastal boulder field at Whalers Way, southern Eyre Peninsula, South Australia, occurs at elevations of 20-30 m above present sea-level on a gently seaward-sloping, karst-weathered calcrete-capped structural bench, formed on the Upper Pleistocene Bridgewater Formation and underlying Carnot Gneisses (Archean-Paleoproterozoic Sleaford Complex). More than 1000 ex situ boulders, cobbles and pebbles of gneiss and mafic igneous rocks, as well as fragments of calcrete, occur within the boulder field and cover an area >6000 m2. All the crystalline rock clasts are derived locally from bedrock outcrops along the adjacent coastline, where metasedimentary granulite-facies of the Carnot Gneisses crop out along shore platforms and their backing cliffs, close to present sea-level. The boulder field is younger than Marine Isotope Sub-Stage 5a (MIS 5a; ca 80 ka) based on amino acid racemisation 'whole-rock' analyses of calcarenite of the Bridgewater Formation, which forms the calcrete bench on which the boulder field rests. The boulder field wraps around the western extremity of cliff-top dunes dated at 18-17 ka by optically stimulated luminescence, implying that the boulder deposit post-dates the formation of the cliff-top dunes. Given that the clasts in the boulder field show minimal weathering rinds, sea-level during the Last Glacial Maximum was some 125 m lower than present and that between 80 and 7 ka ago, sea-level never attained present levels within the region, emplacement of the boulder field by a high-energy wave event in the Holocene highstand, following the 7000 years BP culmination of post-Glacial sea-level rise, is suggested. Storm waves, rather than a tsunami, most likely explain the emplacement of the boulder field.

Click to increase image sizeClick to decrease image size Disclosure statementNo potential conflict of interest was reported by the author(s).

Recent claims based on hydrodynamic modelling within a sequence stratigraphical perspective of incised valley fill sedimentation have argued that the Lower River Murray and its terminal lakes Alexandrina and Albert represented a marine-estuarine lake system, with marine salinities for some 200 km upstream from the Murray Mouth. These claims have encouraged proposals for the removal of barrages near the Murray Mouth to restore the 'original natural condition' of the lakes. It has also been suggested that fine-grained terrestrial sediments were trapped in this mega-lake, necessitating a re-assessment of the Holocene climatic history of southeastern Australia determined from the study of continental slope cores. We show that throughout Holocene time (the past 11.7 ka), the Lower River Murray remained a freshwater-dominated system, based on a range of mutually complementary sedimentary evidence. Radiocarbon dating of Aboriginal middens adjacent to the river and lakes comprising freshwater mussels (dominantly Velesunio ambiguous), crayfish (Euastacus armatus), turtles (Emydura macquarii) and otoliths of freshwater fish species, such as Murray cod (Maccullochella peelii), confirm freshwater riverine and lacustrine conditions throughout the Holocene. Lake Alexandrina also contains endemic obligate freshwater fishes, including a genetically divergent and locally adapted lineage of southern pygmy perch (Nannorpeca australis), revealing an evolutionary history linked to freshwater habitat in the lakes since the late Pleistocene. Freshwater diatoms from fine-grained fluvial clay successions at Riverglen Marina, and diatoms and lacustrine sediments, including sapropels in the lower lakes and their former embayments of Cooke Plains and Waltowa Swamp, also chronicle a history of freshwater deposition. Lakeshore ridges of terrestrially derived quartz sand formed during elevated freshwater lake levels 8.0 +/- 1.2 ka ago, while consolidated masses of the freshwater clam Corbicula australis, radiocarbon dated at 2650 +/- 90 year BP, also attest to long-term freshwater conditions. An open Murray Mouth is prima facie evidence for sustained river discharge, and the mouth remained open throughout the Holocene based on geomorphological evidence. The barrages that were built to retain freshwater within the lower lakes, in response to upstream water abstractions, which had reduced river flows, provide the closest analogue of the 'original' conditions of this environment. With increased automation, nuanced barrage operation could even better simulate the original environment, whereas removing the barrages and building a weir at Wellington would destroy the character of this internationally significant Ramsar Wetland, with detrimental impacts farther upstream.

The Murray River is Australia's longest river, draining the continent's largest exoreic catchment. The river is Australia's most economically valuable, but is highly degraded by water extraction. The Murray River's terminal lakes, Lakes Alexandrina and Albert, formed following the mid-Holocene marine transgression. These lakes are part of one of the most ecologically important wetland ecosystems on the Australian continent and are recognised as internationally significant by the Ramsar Convention. As a result of upstream water extraction, the Lower Lakes are threatened by rising salinity. To combat this threat, water is allocated to maintain the Lower Lakes as freshwater ecosystems. This practice is part of the Murray-Darling Basin Plan, one of the largest environmental water allocation plans in the world. The water allocations and the natural history of the Lower Lakes are the subject of academic and public debate, since the water would otherwise be used for consumptive purposes, particularly irrigated agriculture, upstream. Recent modelling postulated that the lakes were saline for much of the period between 8500 and 5000 years ago. However, using new sedimentary diatom and hydrodynamic modelling evidence, we demonstrate that the Lower Lakes were fresh for most of this time, particularly after 7200 years ago. Elevated Murray River discharge between 7200 and 6600 years ago prevented sea water ingress, despite sea levels +1 m higher than present. After 6600 years ago, the lakes remained predominately fresh. Current management is, therefore, consistent with the lakes' history before European colonisation.

Inselbergs, such as Uluru in central Australia, are iconic landscape features of semi-arid and deeply denuded continental interiors. These islands of rock are commonly skirted by steep, overhanging cliffs (flared slopes) at ground level. The weathering processes responsible for formation of flared slopes and steep-sided inselbergs in flat, planated landscapes are enigmatic. One model emphasizes sub-surface weathering followed by denudation and excavation of saprolite to expose the unweathered bedrock while other models advocate slope development under subaerial conditions at ground level. We present a new hypothesis that identifies wildfire as a primary agent of flared slope development via fire-induced rock spalling around the periphery of inselbergs. Widespread fire-spalling following the 2019–2020 Australian fires illustrates that this is a common form of physical weathering in fire-prone environments but its effects are particularly evident in semi-arid regions where lateral fire-spalling dominates over fluvial and chemical weathering to create flared slopes and steep-sided inselbergs.

Peesey Swamp on southern Yorke Peninsula, southern Australia, is a north-northwesterly-south-southeasterly trending lowland depression, approximately 24 km long and 4 to 10 km wide. The richly fossiliferous mollusc and foraminiferal faunal assemblages of the last interglacial Glanville Formation in Peesey Swamp indicate that the paleoenvironment was a low- to medium-energy, sheltered sandflat to shallow-water seaway during the Last Interglacial Maximum (Marine Isotope Substage [MIS] 5e; 128-116 ka). The presence of the fossil bivalve molluscs Katelysia rhytiphora, Chlamys (Equichlamys) bifrons and Fulvia tenuicostata, in life position, indicate that the paleowater depth was <= 4 m in Peesey Swamp. The seaway cut across southern Yorke Peninsula, establishing a marine connection between southern Spencer Gulf and Investigator Strait during deposition of these taxa. Amino acid racemisation dating of the fossil marine molluscs Katelysia sp. and Fulvia tenuicostata confirms that the shelly assemblages at Peesey Swamp are correlative with the last interglacial Glanville Formation, a succession of richly fossiliferous, mixed quartz-skeletal carbonate sands documented from many sites along the southern Australian coastline. This study illustrates the significant changes in the geographical configuration of coastlines that may accompany relatively modest (<5 m) sea-level changes on low-gradient coastal landscapes.

Quaternary alluvial and colluvial sediments infill major river valleys and form alluvial fans and colluvium-filled bedrock depressions on the range fronts and within the Mount Lofty Ranges of southern Australia. A complex association of alluvial successions occurs in the Sellicks Creek drainage basin, as revealed from lithostratigraphy, physical landscape setting and optically stimulated luminescence (OSL) ages. Correlation of OSL ages with the Marine Oxygen Isotope record reveals that the alluvial successions represent multiple episodes of alluvial sedimentation since the penultimate glaciation (Marine Isotope Stage 6; MIS 6). The successions include a penultimate glacial maximum alluvium (Taringa Formation; 160 +/- 15 ka; MIS 6), an unnamed alluvial succession (42 +/- 3.2 ka; MIS 3), a late last glacial colluvial succession within bedrock depressions (ca 15 ka; MIS 2) and a late last glacial alluvium (ca 15 ka; MIS 2) in the lowest, distal portion of Sellicks Creek. In addition, the Waldeila Formation, a Holocene alluvium (3.5 +/- 0.3 ka; MIS 1), and sediments deposited during a phase of Post-European Settlement Aggradation (PESA) are also identified. The age and spatial distribution of the red/brown successions, mapped as the Upper Pleistocene Pooraka Formation, directly relate to different topographic and tectonic settings. Neotectonic uplift locally enhanced erosion and sedimentation, while differences in drainage basin sizes along the margin of the ranges have influenced the timing and delivery of sediment in downstream locations. Close to the Willunga Fault Scarp at Sellicks Creek, sediments resembling the Pooraka Formation have yielded a pooled mean OSL age of 83.9 +/- 7 ka (MIS 5a) corroborating the previously identified extended time range for deposition of the formation. Elsewhere, within major river valleys, the Pooraka Formation was deposited during the last interglacial maximum (128-118 ka; MIS 5e). In general, alluviation occurred during interglacial and interstadial pluvial events, while erosion predominated during drier glacial episodes. In both cases, contemporaneous erosion and sedimentation continued to affect the landscape. For example, in the Sellicks Creek drainage basin, which lies across an actively uplifting fault zone, late glacial age sediments (MIS 2) occur within the ranges and near the distal margin of the alluvial fan complex. OSL dating of the alluvial successions reported in this paper highlights linkages between the terrestrial and marine environments in association with sea-level (base-level) and climatic perturbations. While the alluvial successions relate largely to climatically driven changes, especially in major river valleys, tectonics, eustasy, geomorphic setting and topography have influenced erosion and sedimentation, especially on steep-sloped alluvial fan environments.

Oxygen isotope-inferred ages as old as the Jurassic have been derived from weathered monzogranite underlying the folded Mount Augustus Sandstone, which forms the massive anticlinal Burringurrah (or Mount Augustus) inselberg, in the Gascoyne district of Western Australia. This large inselberg stands similar to 700 m above the surrounding duricrusted Neogene Gascoyne planation surface at similar to 400 m. The 1150 m thick Mount Augustus Sandstone (c. 1620 Ma), buried by some 10 km of rock of the Edmund and Collier Groups, underwent folding during the Edmundian Orogeny (1030-950 Ma). Abundant Permian glacial deposits throughout western and southern Australia suggest that the landscape was extensively impacted by a continental ice mass during the Gondwanan Permian glaciation, and which provides a maximum age for most recorded chemical weathering profiles within Australia. Nine samples of kaolinite were collected from a 30 m deep exposure of weathered monzogranite cropping out in the core of the anticline beneath the overlying Mount Augustus Sandstone within the topographic amphitheatre of 'The Pound'. Four samples from the profile were analysed, revealing two ages of weathering. The higher samples immediately below the unconformably overlying boulder ferricrete (delta O-18(VSMOW) values of +12.0 and +14.0 parts per thousand imply a Jurassic to early Cretaceous weathering age, while the lower samples (delta O-18(VSMOW) values of +17.6 and +18.3 parts per thousand.) are indicative of a Neogene age. These results suggest downward 'younging' of the profile consistent with a top-down advancing weathering front that developed after uncapping of the anticlinal inselberg and exposure of the underlying monzogranite to surficial chemical weathering. A long-term rate of landscape denudation of similar to 11 m/Ma is estimated from established geological events, rock ages and thicknesses. Dykes and quartz veins suggest that Burringurrah was still deeply buried 500 Ma ago, with the denudation rate indicating exposure of the upper surface of the Mount Augustus Sandstone by similar to 100 Ma. The oxygen isotope data suggest that weathering of the monzogranite beneath the Mount Augustus Sandstone occurred during Jurassic to early Cretaceous times (similar to 200 to 100 Ma), ages broadly coincident with those derived from the application of denudation rates. This suggests that Burringurrah initially developed as an inselberg prior to at least the past 100 Ma. The younger ages from lower parts of the profile suggest that weathering continued into the Neogene/Quaternary (23 Ma to present), during which time the surrounding, now dissected, planation surface was also weathered. (C) 2018 Elsevier B.V. All rights reserved.

Surficial iron-rich deposits (ferricretes) occur on and around Burringurrah (Mount Augustus), a huge, remote inselberg in the Gascoyne district of Western Australia. Oriented NW-SE, Burringurrah is approximately 14 km long, 5 km wide, rises to 1105 m above sea level and stands some 700 m above the surrounding plain. The majority of the ferricretes occupy bedrock valley bottom floors on the southern side of the inselberg at Edney Springs, Flintstone Creek, and on the Edney Trail where they have formed on unweathered quartzose Mount Augustus Sandstone, which only contains a fewpercent Fe2O3. At 'The Pound', a boulder ferricrete overlies deeply weathered igneous bedrock, unroofed by erosion of the overlyingMount Augustus Sandstone, exposing the unconformity between the weathered granitic bedrock and the Mount Augustus Sandstone in the core of a broad, asymmetrical and doubly plunging anticline. On the northern, steeper, side of the mountain, vermiform and conglomeratic ferricretes are sparsely exposed in drainage lines. Ferricretemineralogy is dominated by goethitewith only small amounts of hematite. Oxygen isotope inferred ages of weatheredmonzogranite produced a top-down weathering front extending up to the Neogene at an elevation coincident with the ferricretes within bedrock valley bottoms. Beyond the mountain, the age of ferricreted sandy alluvium was established by thermoluminescence polymineral fine grain dating. These produced a minimum depositional age of >37.6 +/- 2.6 ka and a second finite age of 139 +/- 44 ka, suggesting ferricrete formation heremay have begun during the last interglacial period and continued throughout the late Pleistocene. Formation of ferricretes on top of iron-poor quartzites is unusual. It reflects not only the absolute accumulation of iron oxides derived from the Mount Augustus Sandstone but possibly the additional contributions of iron-bearing aeolian dust from the surrounding plains subsequently washed down drainage lines to accumulate in swampy depressions at the foot of the inselberg. Ferricrete formation was initially simple, with iron in solution impregnating sandy sediment and organic host materials, sporadically impacted by bioturbation by termites. Thin-section petrography reveals an interesting form of in-situ, self-brecciation of quartz and feldspar clasts, which are fractured and infilled with iron oxides and newly precipitated clay which further promotes fragmentation. The mode of ferricrete formation described from Burringurrah is relevant to the laterite-ferricrete debate, for here it is most unlikely that the zones of iron enrichment developed in situ and vertically above the iron-poor quartzite basement as in the sense of the regional 'classic laterite profile'. Crown Copyright (C) 2019 Published by Elsevier B.V. All rights reserved.

Alluvial sequences proximal to coastlines offer opportunities to establish associations between terrestrial, sea-level and climatic events. South Australia hosts a globally significant Pleistocene interglacial sea-level record and numerous terrestrial sediment sources. However, only fragmentary evidence of pre-Last Interglacial alluvium has been identified. This paper presents the first definitive recognition of MIS 7 alluvium in South Australia, which occurs beneath the surface of extensive river terraces flanking Currency Creek and the Finniss River, between the Mount Lofty Ranges and the River Murray Lakes. A thermoluminescence age, 227 +/- 24 ka, correlates with the penultimate interglacial global sea-level highstand. Nearby, last interglacial fossils of the estuarine bivalve Spisula trigonella at 2.53 +/- 025 m APSL occupy a hollow eroded into the MIS 7 alluvium. Increasing aridity and decreased Fluvial activity in the late Quaternary have preserved the MIS 7 alluvium. The fragmentary record of alluvium pre-dating the Last Interglacial is attributed to three principal causes: (1) tectonic subsidence of the Murray Estuary, which increased the potential for burial or coastal erosion of sediments; (2) erosion and reworking of previously existing alluviums, especially during low sea levels of glacial times; (3) the absence of reliable dating controls on the potentially older alluvial sediments.

Yorke Peninsula in southern Australia is an important region for reconstructing relative sea-level histories due to its location on the eastern margin of the tectonically stable Gawler Craton and in one of the world's geographically most remote far-field locations from the Pleistocene ice sheets. Richly fossiliferous, skeletal carbonate sands of the last interglacial (125 ka) Glanville Formation crop out in the coastal cliffs along large sectors of southern Yorke Peninsula. Sedimentary facies include deepening-upward intertidal to shallow subtidal facies, relict storm beach facies and cobble and boulder beach deposits in more exposed, higher energy locations. During deposition of the Glanville Formation, southern Yorke Peninsula had a different coastal geography with two prominent marine corridors extending across the southern-most portion of the entire peninsula. In a 3 km long coastal cliff section in southern Hardwicke Bay, the Glanville Formation crops out as an upward-deepening intertidal-subtidal succession capped by supratidal and subaerially-exposed sediments with pervasive calcrete development. The sedimentary succession passes upwards from a basal unit of intertidal sand flat facies with abundant gastropods (Batillaria diemenensis) near the upper bounding (disconformity) surface, upwards into richly fossiliferous shelly sands (coquina) representing a shallow subtidal facies formed by sediment aggradation in response to a relative sea-level rise. The subtidal facies is dominated by the bivalve molluscs Katelysia sp. and Amesodesma angusta, signifying a water deepening event. The subtidal facies is in turn overlain by pedogenically modified skeletal carbonate sands with pervasive calcrete development signifying a relative sea level fall at the end of the Last Interglacial Maximum. The upper-bounding surface of the shallow-water subtidal facies ranges from 2.4 to 3.0 m Australian Height Datum (AHD) and by analogy with modern sedimentary environments suggests a maximum palaeo-sea level of 4.8 +/- 1.0 m during the Last Interglacial Maximum. Uranium-series ages of 127.3 +/- 2.1 to 115.0 +/- 5.4 ka on specimens of the solitary coral Plesiastrea versipora from the subtidal facies confirm that the succession was deposited during the Last Interglacial Maximum, and are consistent with the independent stratigraphical evidence that the highstand event was represented by a single phase of relative sea-level rise. Correlation with other occurrences of the Glanville Formation in southern Australia has also been confirmed by aminostratigraphy.

ABSTRACT The last interglacial maximum (Marine Isotope Substage 5e [MIS 5e], 128–116 ka) is a distinctive event in recent Earth history. Shoreline successions of this age are important for calibrating climate models and defining the overall behaviour of the crust–mantle system to fluctuating ice and ocean-water volumes. In a global context, the recently intensified interest in last interglacial shoreline successions has revealed considerable variability in the magnitude of sea-level rise during this time interval and highlighted the need to examine paleosea-level evidence from tectonically stable, far-field settings. Situated in the far-field of continental ice sheets and on the tectonically stable Gawler Craton, the 300 km coastal sector of western Eyre Peninsula between Fowlers Bay and Lake Newland in southern Australia represents an important region for defining the glacio-eustatic (ice-equivalent) sea-level attained during the last interglacial maximum based on the relative sea-level observations from this region. Low-energy, shoaling upward, peritidal bioclastic carbonate successions of the last interglacial (locally termed Glanville Formation) formed within back-barrier, estuarine–lagoonal environments in the lee of eolianite barrier complexes (locally termed Bridgewater Formation) along this coastline. The well-preserved shelly successions (coquinas) contain diverse molluscan fossil assemblages including species no longer living in the coastal waters of South Australia (e.g. the Sydney cockle Anadara trapezia and the benthic foraminifer Marginopora vertebralis). The extent of amino acid racemisation (a measure of fossil age based on increasing d/l value) in a range of species, and in particular A. trapezia and Katelysia sp., confirms the time equivalence of the isolated embayment-fill successions, correlated with the informal type section of the Glanville Formation at Dry Creek, north of Adelaide. Preliminary U-series analyses on A. trapezia also suggest a correlation with the last interglacial maximum, but further highlight the complexity in dating fossil molluscs by the U-series method in view of their open-system behaviour. The shelly successions of the Glanville Formation occur at elevations higher than attained by sea-level in the current, Holocene interglacial. A higher sea-level of between 2.1 ± 0.5 and 4 ± 0.5 m above present sea-level is inferred for the last interglacial maximum (MIS 5e) along this coastline based on the elevation of sedimentary successions host to the shallow subtidal–intertidal fossil molluscs Katelysia sp., and Anadara trapezia. The paleosea-level observations place a lower limit on the sea-level attained during the last interglacial maximum and suggest that caution be exercised in the definition of the upper limit of sea-level during this interglacial.

Introduction South Australia is notable for a remarkable diversity of coastal landscapes, many of which are of national and global significance. Numerous landscape-forming processes have influenced the evolution of this coastline. The current shape of the coastline relates to geological processes operating on a wide range of geological timescales that extend as far back as Archaean time (>2.5 billion years). As well as possessing many scenic wonders, the South Australian coastline presents numerous opportunities for scientific investigators to unravel the evolution of the coastline, with national and international implications. As the broader continental-scale features of Australia influence the coastal landscapes of South Australia, the coastline should not be viewed in isolation from its hinterland. Australia in many respects is an old, flat and highly denuded continent, with the lowest topographical relief of all continents. Its intra-plate setting, high degree of tectonic stability, regional aridity, inland drainage (up to half the continent) and absence of major mountain ranges have significantly reduced the supply of terrigenous sediment to much of the coastline of South Australia. Few rivers reach the sea along the entire coastline of South Australia. Much of the State's drainage trends inland, and therefore the production of temperate sedimentary carbonates on the surrounding continental shelves is enhanced. Even on the Adelaide Plains, when the principal rivers (Little Para, Gawler, Light, Wakefield) do flow vigorously, their waters tend to temporarily exceed bankfull discharge and flood the adjacent flood plains, rather than reach Gulf St Vincent. Desert dune fields related to intensified aridity and the latitudinal expansion of the arid zone during successive glacial events4 occur throughout extensive regions of inland Australia and along parts of the coastal margin. At times of glacial low sea level, when South Australia's gulfs were dry land, longitudinal dune fields extended across this broad region. On the northern Adelaide Plains, and to the east of Lake Alexandrina and the northern Coorong Lagoon (Big Desert), as well as on Eyre and Yorke Peninsulas, the dunes are very notable features of the regional landscape, sometimes dramatically truncated at the coast. They have contributed to coastal sediments. General overview The modern coastline: A general overview The modern coastline was broadly established some 7000 years ago with the culmination of the most recent phase of postglacial sea level rise.

Introduction Extending from the Western Australian border near Wilson Bluff to Cape Carnot and Cape Wiles, south of Port Lincoln, this section of coast covers approximately 1400 km. Although it is the longest section of coastline described in this book, it has sufficient integrity to consider it a discrete unit. The west coast of Eyre Peninsula forms the eastern side of the Great Australian Bight, the general shape of which was inherited from the continental rifting and separation from Antarctica some 43 Ma ago. There is not a perfect jigsaw fit of the current Australian and Antarctic coasts, but if the edges of the continental shelves, which separate continental and oceanic crust, are used, then the fit is much better. All of the coastline is underlain by crystalline rocks (granites, gneisses, volcanic rocks and metamorphosed sediments) of the ancient and highly stable Gawler Craton (Figure 10.1). The Bight coastline has remained tectonically stable during the Pleistocene. On Eyre Peninsula there is no spectacular sequence of Pleistocene coastal dune barriers as in the southeast of South Australia, where the land has been progressively uplifted to record successive interglacial high sea levels. The stability of the Gawler Craton, which underlies Eyre Peninsula, caused succeeding interglacial high sea levels to merge, rework and overlap with the previous ones. However, distinct Eocene shorelines in the Eucla Basin are marked by coastal barrier systems similar to the modern Murray Mouth and Coorong, forming relict strandlines, lagoons, estuaries, coastal barriers and extensive coastal sand dunes and beach ridges some 300 km inland of the modern coastline (Figure 10.2). Ongoing stability of the coast since the Last Interglacial (132 to 118 ka) is indicated by the constant elevation of marine shells of that age along the shoreline. Marine shells including the subfossil Anadara trapezia occur at a consistent height of near 2 m APSL, so they have been little affected by land movements, as they have in other parts of the State. The presence of Anadara indicates that inner shelf waters were warmer, accentuated by an enhanced Leeuwin Current, which moves south along the western side of Australia before flowing easterly along the Great Australian Bight. Aeolianite (dune calcarenite) blankets the landscape along the coast and well inland. Aeolianite consists of former coastal sand dunes up to 100 m high which have been lithified (that is, turned into a harder rock).